Expanding, Conforming Interbody Spacer

ABSTRACT

An expanding, conforming interbody implant includes a plurality of superior and a plurality of inferior segments. The segments are adapted to individually expand, contact, and conform to endplates of vertebral bodies to distribute forces equally over the implant and across the vertebral endplates. Once a proper extension of the segments has been achieved, the segments are locked in position. The implant has a stiffness that approximates the stiffness of bone, and the implant minimizes problems with subsidence, endplate fractures, and stress shielding.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/736,924, filed Sep. 26, 2018, and U.S. Provisional Application No.62/751,432, filed Oct. 26, 2018.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to surgical implants, and moreparticularly to interbody spacers for vertebral implants.

2. Background and Related Art

In the area of spinal implants, there are certain difficulties thatremain unaddressed. In particular, the problems of subsidence, endplatefractures, and stress shielding remain problems that can causeintervertebral implants to fail or to have reduced effectiveness atachieving the desired implant goals. These problems are heightened bythe difficulties in properly sizing implants: to ensure that a correctlysized implant is used, the doctor must be careful in selecting amongavailable implants, and there are costs associated with carryingimplants of multiple sizes to be available at the time of implantsurgery. Accordingly, either the doctor or hospital must incur the costof purchasing and holding in inventory a large number of implants ofvarying sizes to ensure that a correctly sized implant is available, orthey must have a reduced number of implant sizes with the risk that animplant of the correct size will not be available, such that anincorrectly sized implant must be used with reduced effectiveness.

Additionally, depending on surgeon experience, it may be difficult forthe surgeon to select among available implant sizes an implant of idealsize, and some trial-and-error efforts may be used to select amongavailable implant sizes. Where this is done, however, either incorrectlysized, but tried, implants are contaminated and wasted, or are requiredto pass through a sterilization process before being reused, if evenpossible. Accordingly, such trial-and-error efforts result in increasedcosts to the surgeon and/or hospital, which must then be passed on topatients.

Even when surgeons are able to use correctly sized implants, suchimplants still rarely have proper physical characteristics to promotebone ingrowth and to minimize problems with subsidence, endplatefracture, and/or stress shielding. Current implants are rarely shaped toconform to the endplates where they are placed. Additionally, currentimplants typically have stiffnesses that are significantly differentfrom the stiffness of the vertebral endplates where they are placed,such that any nonconformities between the endplates and the implant leadto locations of increased stress and implant failure.

Accordingly, for reasons such as these, existing interbody implants failto satisfactorily meet the requirements desired by surgeons andpatients.

BRIEF SUMMARY OF THE INVENTION

Implementations of the invention provide expandable, conformableinterbody spacers, methods for manufacturing interbody spacers, andmethods for using interbody spacers. In accordance with certainimplementations of the invention, an expandable, conformable interbodyimplant includes a frame, a first plurality of endplate-contactingsegments adapted to extend in a superior direction from the frame, asecond plurality of endplate-contacting segments adapted to extend in aninferior direction from the frame and a locking mechanism adapted tolock the first plurality of endplate-contacting segments and the secondplurality of endplate-contacting segments in a variety of extendedpositions.

In some implementations, the first plurality of endplate-contactingsegments is adapted to contact and collectively conform to an inferiorendplate of a first vertebral body and wherein the second plurality ofendplate-contacting segments is adapted to contact and collectivelyconform to a superior endplate of a second vertebral body. In someimplementations, a load between the inferior endplate and the anteriorendplate is substantially equally distributed among the first and secondpluralities of endplate-contacting segments.

In some implementations, the locking mechanism exerts a lateralcompression force among the first and second pluralities ofendplate-contacting segments. In some implementations, the lockingmechanism exerts a lateral compression force between the first pluralityof endplate-contacting segments, the second plurality ofendplate-contacting segments, and a plurality of cross webs.

In some implementations, the first and second pluralities ofendplate-contacting segments have a limited amount of lateral motionwithin the frame before the locking mechanism is engaged to lock thefirst and second pluralities of endplate-contacting segments in theirextended positions. In some implementations, when the first and secondpluralities of endplate-contacting segments are in a retracted position,the implant has a smaller vertical profile for insertion.

In some implementations, the first and second pluralities ofendplate-contacting segments are each interlocked with adjacent segmentswhile permitting relative superior-inferior motion therebetween. In someimplementations, the first and second pluralities of endplate-contactingsegments each include a plurality of segments extending along a lengthof the implant. In some implementations, the first and secondpluralities of endplate-contacting segments each include a plurality ofsegments extending across a width of the implant.

In some implementations, the first and second pluralities ofendplate-contacting segments have a stiffness approximating thestiffness of vertebral bone. In some implementations, the first andsecond pluralities of endplate-contacting segments have a coil packconstruction.

In some implementations, the implant is formed of biocompatiblesubstances.

In some implementations, the implant includes an expansion mechanismadapted to apply a superior-directed force to each of the firstplurality of endplate-contacting segments and an inferior-directed forceto each of the second plurality of endplate-contacting segments beforethe locking mechanism is engaged. In some implementations, the expansionmechanism is adapted to continue providing the superior-directed forceand the inferior-directed force while the locking mechanism is engaged.In some implementations, the expansion mechanism includes a bladderdisposed in an internal cavity of the implant. In some implementations,the expansion mechanism is a mechanism such as a bladder, a plurality ofcorrugated layers adapted to be moved between nested and offsetpositions, a plurality of springs, a wire disposed on a plurality ofpulleys, a plurality of threaded cylinders, or a plurality of dimpledlayers adapted to be moved between nested and offset positions.

In some implementations, the frame includes openings on opposite endsthereof to permit access to an internal space of the implant. In someimplementations, the implant is adapted to permit application ofincreased forces in any of an anterior area, a posterior area, a rightlateral area, or a left lateral area.

According to further implementations of the invention, a method forusing an expanding, conforming interbody implant, includes a step ofaffixing an expanding, conforming interbody implant to an inserter, theimplant including a frame, a first plurality of endplate-contactingsegments adapted to extend in a superior direction from the frame, asecond plurality of endplate-contacting segments adapted to extend in aninferior direction from the frame, and a locking mechanism adapted tolock the first plurality of endplate-contacting segments and the secondplurality of endplate-contacting segments in a variety of extendedpositions. The method also includes steps of placing the implant in adesired location using the inserter while the first and secondpluralities of endplate-contacting segments are in a retracted position,supplying a force that causes the first and second pluralities ofendplate-contacting segments to extend and generally conform to surfacesabove and below the implant, and engaging the locking mechanism tosecure the first and second pluralities of endplate-contacting segmentsin extended and conforming positions.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The objects and features of the present invention will become more fullyapparent from the following description and appended claims, taken inconjunction with the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are,therefore, not to be considered limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIGS. 1A and 1B show perspective views of an illustrative implant;

FIG. 2 shows a perspective transparent view of an illustrative implant;

FIG. 3 shows a perspective partially-transparent view of an illustrativeimplant;

FIG. 4 shows a perspective view of an illustrative implant;

FIG. 5 shows a perspective partially-transparent view of an illustrativeimplant;

FIG. 6A-6E show perspective views of various mechanisms to interlocksegments of an implant;

FIGS. 7A-7F show perspective views of various methods for interlockingsegments of an implant;

FIGS. 8A and 8B show manners to expand an implant;

FIGS. 9A-9C show manners to expand an implant;

FIG. 10 shows an exploded view of a representative bladder;

FIG. 11 shows a perspective view of a portion of an implant;

FIG. 12 shows a perspective view of an implant;

FIG. 13 shows a perspective view of an implant;

FIGS. 14A-14C show perspective views of an implant;

FIGS. 15A-15C show perspective views of implants and components ofimplants;

FIGS. 16A-16D illustrate methods for expanding segments of an implant;

FIGS. 17A-17C illustrate aspects of an implant;

FIGS. 18A-18C illustrate features of certain implants;

FIG. 19 illustrates one construction of a block of an implant;

FIGS. 20A-20D illustrate implants and components thereof;

FIGS. 21A-21B illustrate aspects of certain embodiments of an implant;

FIGS. 22A-22D illustrate views of an alternate embodiment of an implant;

FIGS. 23A-23C illustrate mechanisms for locking segments of an implant;

FIGS. 24A-24D illustrate an alternate implant and enlarged viewsthereof;

FIGS. 25A and 25B illustrate aspects of an implant;

FIGS. 26A and 26B illustrate aspects of an implant;

FIGS. 27A and 27B illustrate aspects of an implant and an implantinserter;

FIGS. 28A and 28B illustrate aspects of an implant inserter;

FIGS. 29A and 29B illustrate aspects of implant inserters;

FIGS. 30A and 30B illustrate aspects of implant inserters; and

FIG. 31 illustrates aspects of an implant inserter.

DETAILED DESCRIPTION OF THE INVENTION

A description of embodiments of the present invention will now be givenwith reference to the Figures. It is expected that the present inventionmay take many other forms and shapes, hence the following disclosure isintended to be illustrative and not limiting, and the scope of theinvention should be determined by reference to the appended claims.

What is needed is an interbody implant with the ability to conform tothe endplate shape, thereby minimizing problems of subsidence, endplatefracture, and stress shielding. Such an implant may utilize expandingsegmented portions to permit the surfaces of the implant to generallyconform to the vertebral endplates above and below the interbody space.Additionally, an interbody implant with an ability to expand reduces thecarrying or inventory cost of the hospital and/or surgeon while alsoreducing the need for trialing by the surgeon. When such implants alsoinclude correct stiffness, they further reduce the possibility ofsubsidence, endplate fracture, or stress shielding.

Embodiments of the invention provide expandable, conformable interbodyspacers, methods for manufacturing interbody spacers, and methods forusing interbody spacers. In accordance with certain embodiments of theinvention, an expandable, conformable interbody implant includes aframe, a first plurality of endplate-contacting segments adapted toextend in a superior direction from the frame, a second plurality ofendplate-contacting segments adapted to extend in an inferior directionfrom the frame and a locking mechanism adapted to lock the firstplurality of endplate-contacting segments and the second plurality ofendplate-contacting segments in a variety of extended positions.

In some embodiments, the first plurality of endplate-contacting segmentsis adapted to contact and collectively conform to an inferior endplateof a first vertebral body and wherein the second plurality ofendplate-contacting segments is adapted to contact and collectivelyconform to a superior endplate of a second vertebral body. In someembodiments, a load between the inferior endplate and the anteriorendplate is substantially equally distributed among the first and secondpluralities of endplate-contacting segments.

In some embodiments, the locking mechanism exerts a lateral compressionforce among the first and second pluralities of endplate-contactingsegments. In some embodiments, the locking mechanism exerts a lateralcompression force between the first plurality of endplate-contactingsegments, the second plurality of endplate-contacting segments, and aplurality of cross webs.

In some embodiments, the first and second pluralities ofendplate-contacting segments have a limited amount of lateral motionwithin the frame before the locking mechanism is engaged to lock thefirst and second pluralities of endplate-contacting segments in theirextended positions. In some embodiments, when the first and secondpluralities of endplate-contacting segments are in a retracted position,the implant has a smaller vertical profile for insertion.

In some embodiments, the first and second pluralities ofendplate-contacting segments are each interlocked with adjacent segmentswhile permitting relative superior-inferior motion therebetween. In someembodiments, the first and second pluralities of endplate-contactingsegments each include a plurality of segments extending along a lengthof the implant. In some embodiments, the first and second pluralities ofendplate-contacting segments each include a plurality of segmentsextending across a width of the implant.

In some embodiments, the first and second pluralities ofendplate-contacting segments have a stiffness approximating thestiffness of vertebral bone. In some embodiments, the first and secondpluralities of endplate-contacting segments have a coil packconstruction.

In some embodiments, the implant is formed of biocompatible substances.

In some embodiments, the implant includes an expansion mechanism adaptedto apply a superior-directed force to each of the first plurality ofendplate-contacting segments and an inferior-directed force to each ofthe second plurality of endplate-contacting segments before the lockingmechanism is engaged. In some embodiments, the expansion mechanism isadapted to continue providing the superior-directed force and theinferior-directed force while the locking mechanism is engaged. In someembodiments, the expansion mechanism includes a bladder disposed in aninternal cavity of the implant. In some embodiments, the expansionmechanism is a mechanism such as a bladder, a plurality of corrugatedlayers adapted to be moved between nested and offset positions, aplurality of springs, a wire disposed on a plurality of pulleys, aplurality of threaded cylinders, or a plurality of dimpled layersadapted to be moved between nested and offset positions.

In some embodiments, the frame includes openings on opposite endsthereof to permit access to an internal space of the implant. In someembodiments, the implant is adapted to permit application of increasedforces in any of an anterior area, a posterior area, a right lateralarea, or a left lateral area.

According to further embodiments of the invention, a method for using anexpanding, conforming interbody implant, includes a step of affixing anexpanding, conforming interbody implant to an inserter, the implantincluding a frame, a first plurality of endplate-contacting segmentsadapted to extend in a superior direction from the frame, a secondplurality of endplate-contacting segments adapted to extend in aninferior direction from the frame, and a locking mechanism adapted tolock the first plurality of endplate-contacting segments and the secondplurality of endplate-contacting segments in a variety of extendedpositions. The method also includes steps of placing the implant in adesired location using the inserter while the first and secondpluralities of endplate-contacting segments are in a retracted position,supplying a force that causes the first and second pluralities ofendplate-contacting segments to extend and generally conform to surfacesabove and below the implant, and engaging the locking mechanism tosecure the first and second pluralities of endplate-contacting segmentsin extended and conforming positions.

Existing interbody implant designs have at most one or two movingelements, allowing at best for two points of adjustment (e.g., heightand lordosis). The innovative designs of embodiments of the implant 10discussed herein use multiple height-independent segments 12 to conformto individuals' endplate shape, as is illustrated in FIGS. 1A and 1B.FIG. 1A illustrates one embodiment of the implant 10 having a pluralityof height-independent segments 12 divided along the length of theimplant. The illustrated embodiment shows how segments 12 are placed onboth upper and lower surfaces of the implant 10 to allow conformity toboth superior and inferior endplates of the intervertebral space.

FIG. 1B illustrates a portion of another embodiment of the implant 10having a plurality of height-independent segments 12 divided along boththe length and width of the implant. While not shown in this embodimentin FIG. 1B, the full implant 10 would have such segments 12 on both theupper and lower surfaces of the implant 10 to permit implant conformityto both the superior and inferior endplates of the intervertebral space.

Even where prior adjustable-height implants provided some adjustabilityfor height or lordosis, the mechanisms for such adjustability hadsignificant downsides. In particular, it was typical for such implantsto use the same mechanical feature for lifting the implant or adjustingthe height as for holding and carrying the patient load. This mechanicalfeature might be a ramp, wedge, or the like, but tended to collect theload to a very small portion of the implant, requiring it to beextremely strong and stiff, leading to subsidence and stress shielding.

Embodiments of the invention separate the conforming mechanism (the liftmechanism) from the shape-locking or height-locking mechanism. Thisseparation allows the implant to have a reduced stiffness in thebiological load path, thereby allowing the implant 10 to more-closelyapproximate the stiffness of bone. As illustrated in the embodimentshown in FIG. 2 , in some embodiments, the segments 12 are lifted orseparated into conformance with the vertebrae by a lift mechanism suchas an inflatable bladder (not shown). Once the segments 12 are at thedesired location (e.g., achieving a desired height and/or lordosis), aframe 14 of the implant 10 surrounding the segments is translatedrelative to the segments 12, such that teeth 16 of the lateral edges ofthe segments 12 engage corresponding teeth on portions of the insidesurface of the frame 14, thereby providing multiple less-rigid loadpaths between the opposing segments 12 (e.g., in the superior-inferioraxis). If desired in some embodiments, the lift mechanism may then beremoved from the implant 10.

As another example, as illustrated in FIG. 3 , in alternate embodiments,each segment 12 has a strut (indicated by the arrows) along each sidethereof. The struts of adjacent segments 12 interdigitate with struts ofsegments 12 on the other side of the implant 10 (superior strutsadjacent to inferior struts). A light clamping force through the stackof struts (e.g., in the lateral axis), the conformed shape is locked andsuperior-inferior loads are transmitted locally from endplate toendplate, rather than being collected into a single overly rigidstructure.

By providing a design where forces are transmitted through the implant10 in as many paths as possible, rather than by collecting forces into asingle rigid frame structure, stress shielding is reduced. This isillustrated in FIGS. 5 and 6A-6E, which illustrate how embodiments ofthe implant 10 permit the distribution of load along a variety of loadpaths 18 from the conforming superior surface of the implant 10 to theconforming inferior surface of the implant 10.

Embodiments of the invention embrace the use of additive manufacturingtechniques (e.g., 3D printing) that allow achievement of various designobjectives, including the manufacture of interlocking segments 12 thatremain interlocked but permit some measure of sliding relative to eachother such that the individual segments 12 can conform to the vertebralendplates. In some embodiments, other than additive manufacturingtechniques are used to manufacture some or all of the implant 10,including the segments 12 and/or the frame 14. In other embodiments,additive manufacturing techniques are used to manufacture both thesegments 12 and the frame 14. Accordingly, embodiments of the inventionare not limited to a single manufacturing technique.

FIGS. 6A-6E illustrate various illustrative embodiments of manners inwhich adjacent segments 12 may be made interlocking while allowing acertain amount of sliding motion relative to each other in a generallysuperior-inferior direction. Other manners of providing slidableinterlocking have been illustrated in FIGS. 1-5 , and the mannersillustrated in the Figures are not intended to be exhaustive, butillustrative of manners in which slidable interlocking of adjacentsegments may be achieved.

As illustrated in FIG. 6A, adjacent segments 12 of one type ofembodiment are joined to different elements of nested coils, allowingrelative translation, but preventing lateral separation of segments 12.As illustrated in FIG. 6B, adjacent segments 12 of another type ofembodiment are joined by pin-slot features 22 that again allow relativetranslation but prevent lateral separation of segments 12. Asillustrated in FIG. 6C, adjacent segments 12 of another type ofembodiment are joined by a grid of torsion bars 24 that also helpbalance the load across the implant surface. As illustrated in FIG. 6D,adjacent segments 12 of another type of embodiment includesmall-diameter coils 26 linked by larger-diameter coils 28 to form animplant surface, as illustrated in more detail in FIGS. 17A-17C. Asillustrated in FIG. 6E, adjacent segments 12 of another type ofembodiment are joined by compliant flexures 30.

FIGS. 7A-7F illustrate various alternative illustrative embodiments ofmanners in which adjacent segments 12 may be made interlocking whileproviding a certain amount of sliding motion relative to each other in agenerally superior-inferior direction. FIG. 7A illustrates one way inwhich a surface of the implant 10 may be formed of interlocking chainmail links 32 in some embodiments. FIG. 7B illustrates one way in whichsegments 12 may be formed to have interlocked bars 34 in certainembodiments. FIG. 7C illustrates one way in which adjacent segments 12may have articulating joints 36 in some embodiments. FIG. 7D illustratesone manner in which adjacent segments 12 may be formed with dovetailjoints 38 in some embodiments. FIG. 7E illustrates one way in whichadjacent segments 12 may be formed with interlocking shapes 40 incertain embodiments. FIG. 7F illustrates on manner in which adjacentsegments 12 may be formed with corresponding T-slots 42.

As discussed previously, prior expandable interbody implants cannotconform effectively because they typically have a single lift mechanism(e.g., a ramp, a wedge, or the like) that performs all the lifting at asingle point. Embodiments of the present invention, however, providelifting at multiple points to achieve conformance with the shape of thevertebral endplates. In certain embodiments of the invention, the liftmechanism is configured to apply equal lift force or bone contactpressure at all segments 12.

In certain embodiments, the lift mechanism includes an inflatableballoon or bladder (similar to a kyphoplasty balloon) temporarily orpermanently disposed within a central cavity of the implant. After theimplant 10 is placed in the vertebral space, the inflatable balloon orbladder is inflated until the segments 12 contact the endplates of thevertebrae, and additional inflation may be provided to achieveadditional height and/or lordosis. Then, the adjustment of the segments12 is locked, such as using one of the methods discussed herein, and theballoon or bladder may be deflated and potentially removed from theimplant.

FIGS. 8A and 8B illustrate alternate methods for providing distributedlifting to segments 12 of embodiments of the implant 10. According tothe method illustrated in FIG. 8A, a tension wire, such as a nitinolwire 44 acts on pulleys 46 on opposite-facing segments 12, such that thesegments 12 can lift with equal force per segment 12. In another type ofembodiment, illustrated in FIG. 8B, the implant 10 is built up fromcorrugated layers 48, where each layer 48 is allowed to conform by beingspringy. In such embodiments, a collapsed height is achieved whenalternating layers are shifted and allowed to nest, and a raised heightis achieved by shifting the alternating layers to an offset positionsuch as is shown in FIG. 8B.

FIGS. 9A-9B illustrate certain alternate methods for providingdistributed lifting to the various segments 12 of the implant 10. Inembodiments such as illustrated in FIG. 9A, a central plate 50 has slitswhich pinch on rails on each segment 12. As the central plates 50 areseparated, the attached segments 12 move with the central plates 50;however, when the force on any segment 12 exceeds the friction generatedby the pinch force (e.g., when that segment 12 contacts the vertebralplate with sufficient force), that segment 12 stops traveling. Othersegments continue traveling until a conformed shape and distributed loadhave been achieved, wherein positions of the segments are locked aspreviously discussed.

In embodiments such as illustrated in FIG. 9B, stacks of diamond- oralmond-shaped springs 52 may be provided in the implant 10. When thesprings 52 are forced into each other laterally, they will expandvertically. A single force applied to the end of the stack causes allthe stacks to experience an expansion and lift. In embodiments such asillustrated in FIG. 9C, each segment 12 may be provided with its ownspring 54 to lift it into contact with the bone of the vertebralendplate. In some such embodiments, the segments 12 are held in aretracted position, compressing the springs 54, until the implant 10 isin a desired position, after which the segments 12 can be released toallow the springs 54 to cause the segments to expand and lift, therebyconforming to the vertebral endplates.

FIG. 10 illustrates in exploded view one embodiment of ashape-controlled bladder or balloon (hereafter bladder 56) adapted toprovide lift or separation to the segments 12 of the implant 10. In thisand similar embodiments, the bladder 56 is formed of multiple layersthat allow the bladder 56 to expand vertically (in the superior-inferiordirection) while self-constraining against unwanted lateral expansion,which would put unnecessary loads on the frame 14. Kyphoplasty balloonstend to expand equally in all directions, but for an expanding interbodyimplant, it would be more desirable for the bladder 56 to only (orlargely only) expand vertically. In the illustrated embodiment, thebladder 56 is formed of various layers that are bonded on alternateedges (inner and outer edges) to form a bellows-like construction, andthe layers have internal reinforcement that prevents or reduces lateralexpansion. In alternate embodiments, other internal reinforcementsprevent or minimize lateral expansion.

Initially, the bladder 56 is sized to fit in a flat, rectangular cavity.In some embodiments, the bladder 56 is designed to receive two cycles ofinflated pressure of approximately 400 pounds per square inch (psi)(approximately 2,800 kilopascals (kPa)) for five minutes each, orapproximately 200 psi (approximately 1,400 kPa) for one hour. Thebladder 56 of some embodiments is flexible enough to be removed from anapproximately 0.150 inch to approximately 0.170 inch (approximately 3.81to approximately 4.32 mm) hole. The dimensions of the cavity will varybased on implant footprint and height, but in one illustrativeembodiment, the cavity has dimensions approximately as follows (prior toinflation of the bladder 56): a length of approximately 0.743 inches(approximately 18.9 mm), a width of approximately 0.308 inches(approximately 7.82 mm), and a height of approximately 0.036 inches(approximately 0.914 mm). The access hole for the implant 10 in thisillustrative embodiment may be approximately 0.170 inches in diameter(approximately 4.32 mm in diameter), and a feed tube for the bladder 56may be approximately 0.105 inches in diameter (approximately 2.67 mm indiameter).

In some embodiments, the implant 10 is configured to provide anadjustable base height for the implant, with conformability at aselected height. An example of such an embodiment is illustrated atFIGS. 11-13 . FIG. 11 shows that the embodiment of the implant includestwo frame halves 60. Each frame half 60 carries a set of static blocks62 which move with the frame half 60 in superior/inferior direction, butare able to slide laterally in the frame half 60. The implant 10 alsoincludes height bars 64 that include ramps that interact with ramps onthe frame halves to increase and/or measure the base height of theimplant 10.

FIG. 12 shows additional components of the implant assembly, namelymoving blocks 66. The internal bladder 56 (not shown) causes the movingblocks 66 to conform to the vertebral endplates. The internal bladder 46may also contribute to the force causing the increase in the base heightof the implant. Once conformity to the endplate has been achieved, endscrews 68 are tightened to compress the static and moving blockstogether and lock the conformed shape. Thereafter, the bladder 56 may beremoved and replaced with a compliant core, as illustrated in FIG. 13 .In some embodiments, the height bars 64 may be released to allow theimplant 10 to settle onto the compliant core (e.g., the static blocks 62rest on the compliant core and transfer forces therethrough).

FIGS. 14A-14C illustrate another type of embodiment of the implant 10,this embodiment being a multi-piston embodiment that has acompliant/porous frame 70. The frame 70 is fitted with multiplecross-members 72, as illustrated in FIG. 14A. The cross members 72 areable to translate a short distance laterally within the frame 70. Theimplant 10 also includes displacement-limited pistons 74 between thecross members 72. The bladder 56 (not shown) is inserted between theupper and lower layers of pistons 74. Under pressure from the bladder56, the pistons 74 move outward to conform to the vertebral endplate andprovide a distraction force, as illustrated in FIG. 14C. (FIG. 14C doesnot illustrate movement of the lower pistons 74, but such pistons 74would be present and move as well.) Once movement of the pistons 74 iscomplete and to be locked, screws 76 (or some other mechanism) may beactuated to compress the cross members 72 and pistons 74 to frictionallylock the conformed shape and height. The inserter tool and bladder 56are removed and the implant 10 is post-packed with bone graft material,etc., if desired.

In additional embodiments, the implant 10 includes multiple compliantsegments 12 supported by fingers 78, as illustrated in FIG. 15A. Thefingers 78 of upper segments 12 slide on fingers 78 of lower segments 12on adjacent surfaces. Multiple segments 12 lock together in a fullimplant, as shown in FIGS. 15B and 15C (illustrating varying embodimentsof the implant 10). During implantation, the bladder 56 causes thesegments 12 of the implant 10 to assume the conformed shape and providesa distraction force. Then, screws 80 or some other locking mechanism isactuated to compress all fingers 78 together (e.g., through the lateralload path illustrated in FIG. 15C) to frictionally lock the fingers 78and thus the segments 12 together to maintain the conformed shape andheight. The bladder 56 is removed and post packing occurs, if desired.

In alternate embodiments of the implant, something other than thebladder 56 is used as a lift mechanism. In some embodiments, a centralarea of the implant 10 is filled with a biocompatible but extremelyhydrophilic material. After implantation, a saline solution is appliedto the hydrophilic material such that the material swells at a certainpressure to cause the segments 12 of the implant to conform and lift ina manner similar to the manners illustrated and described herein.

FIGS. 16A-16C illustrate other mechanisms that may be used withembodiments of the invention. FIG. 16A illustrates a threaded cylindersegment 82 with portions containing a right-hand thread and otherportions containing a left-hand thread. A simple rotation causes thecylinder segment 82 to simultaneously apply upward and downward forces,and can also cause locking. Multiple instances of the cylinder segment82 would be used in each implant 10.

FIGS. 16B-16D illustrate how dimpled moveable layers 84 can beinterleaved and nested then translated relative to each other to provideheight control. By selecting and zoning the location of dimples todifferent areas of the moveable layers 84, the implant 10 may beprovided with height control of left/right as well as anterior/posteriorareas of the implant 10 as the surgeon may desire during implantation.Static layers 86 of the implant 10 may be toothed together, asillustrated in FIG. 16D to preserve the implant footprint acrossvariations in implant height.

FIGS. 17A-17C illustrate an example of embodiments in which interlockingcoils form the conforming surfaces of the implant 10. In this type ofembodiment, interlocking small-diameter coils 26 and large-diametercoils 28 are created in upper sets 88 and lower sets 90. The upper sets88 and the lower sets 90 are located in a dual-slot frame 92, with thesmall-diameter coils 26 of the upper sets 88 interdigitated with thesmall-diameter coils 26 of the lower sets 90. The implant 10 is insertedwhile in the position shown in FIG. 17A, then the upper sets 88 and thelower sets 90 are expanded in a fashion similar to that disclosedherein, and the height is locked by compressing (laterally) theinterdigitated smaller-diameter coils 26, as shown in FIG. 17B. FIG. 17Cshows the interlocking coils in more detail. The interlocking coils canbe extended in their conformability by not typing the multiple leads ofthe same coils together, which leads to multiple nested structures whicheach have their own compliance and can translate on each other.

FIG. 18A illustrates how in some embodiments, a coil structure 94 couldbe disposed laterally instead of vertically (as illustrated in FIGS.17A-17C) to create a conformable surface. FIG. 18B illustrates that insome embodiments, an implant 10 includes a plurality of rings 96 tunedto have a correct stiffness. FIG. 18C illustrates that where a rampmechanism 98 is used to cause height increases of the implant 10(thereby reducing the inventory/carrying cost for carrying implants ofvarying height), and where space does not permit the ramp mechanism 98to give the implant full height in a single stroke, shims 100 can beinserted between strokes to increase the height variability of theimplant 10.

FIG. 19 illustrates one manner of constructing the compliant blocks ofthe embodiments illustrated in FIGS. 11-13 . The manner of constructingillustrated in FIG. 19 may be used for both the static blocks 62 and themoving blocks 66. The construction method uses multiple nested coils asdescribed in U.S. Patent Application Publication No. 2017/0156880 toHalverson and Hawkes, published on Jun. 8, 2017, which is incorporatedherein by reference for all it discloses. The diameter of the nestedcoil structure illustrated in FIG. 19 may be smaller than that disclosedin the prior publication so as to improve spatial density and coilstability in a small structure.

FIG. 20A illustrates an alternate type of embodiment of the implant 10.In this type of implant 10, the stack of segments 12 is lightly loadedwith a clamping force. The lifting mechanism incrementally lifts eachsegment 12 to a given height, then the lifting mechanism is withdrawn.Any segments 12 experiencing a load greater than the frictional forceexerted by the initial clamping mechanism will then retreat until othersegments 12 come into contact with the bone and the load is evenlydistributed over the segments 12. The clamping force is then increasedto a final value to fix the shape and height of the implant 10 and itssegments 12. Post packing of bone graft material, etc., may then occuras desired.

FIGS. 20B-20D illustrate another type of embodiment, in whichinterdigitation is extended with one or more middle layers 102 such thatthe segments 12 on each side of the implant 10 can move out farther andstill be shape locked. In such embodiments, there are two clampingpaths, as illustrated by the arrows shown in FIG. 20C. In someembodiments, the clamping paths can be varied in orientation, asillustrated by the arrows of FIG. 20D.

In some embodiments, a sliding caliper could be used to measure theendplate shape and build a custom implant 10 out of compliant segmentsof a correct height, as illustrated in FIG. 21A. In some embodiments, aspecial inserter could be used to assemble the implant 10 in situ,thereby retaining the small-access benefits of the implant 10 beingexpandable.

FIG. 21B illustrates that in some embodiments, the screw-based mechanismfor locking stacks of blocks or fingers can be replaced with cams,ramps, or wedges.

FIGS. 22A-22D illustrate a type of embodiment where the implant 10 isformed of multiple compliant layers 104 that clamp against each otherand against a ground layer to maintain an arched/bridged/conformedshape. FIGS. 22A-22C each illustrate a configuration of alternate layers104, and FIG. 22D illustrates an embodiment of the assembled implant 10.

FIGS. 23A-23C illustrate alternate types of clamping mechanisms (otherthan screws such as end screws 68 or screws 76 or 80) to permit lockingof the height of the implant 10. In the illustrative embodiment of FIG.23A, the implant 10 is provided with a face thread 106 instead of amale-female thread to avoid the radial space loss of the thread overlaparea. Such an embodiment provides for a larger driver and better accessfor the bladder 56 and post packing with graft material than a singlemale-female thread. The face thread 106 can be left handed on one faceand right handed on the other face to reduce the ramp angle of thethread and thus reduce frictional losses. Multiple starts are possibleto save space as well.

In some embodiments, as is illustrated in FIGS. 23B and 23C, aconventional threaded locking mechanism can be replaced by aquarter-turn mechanism which always locks to the same kinematicposition, thereby saving the surgeon the trouble of worrying that he orshe didn't tighten the screws enough or that some factor caused a driveto torque out too early.

As discussed above, embodiments of the implant may be manufactured usingadditive manufacturing methods. In such embodiments, clearance betweenadjacent parts is tuned such that the implant 10 can be manufactured(e.g., printed) as an assembled unit without having adjacent surfacesfuse. FIGS. 24A-24C illustrate considerations that may be used indetermining clearances between adjacent parts during fabrication. FIG.24A shows an embodiment of the implant 10. FIG. 24B shows a close-upview of the implant 10 of FIG. 24A, showing that clearance will beconsidered between a segment 12 and its containing pocket, between asegment 12 and its adjacent segments 12, between a segment 12 and anytravel limiters, between a cross bar and the frame 14 of the implant 10,and between the frame 14 and an end bar. The clearances required may bedifferent at each location.

For improved avoidance of component fusion between adjacent parts during3D printing, the implant 10 can be designed with a separate end portion108, as shown in FIG. 24C. The implant 10 is printed without the endplate 108 and with the segments 12 and cross webs spaced out. Aftersupport removal, the end plate 108 can be inserted and held in place bymechanical means or by welding or bonding, as also illustrated in FIG.24C. In some embodiments, the end plate can be fabricated in an invertedor arc shape that comes into a desired planar shape when loaded by thelocking mechanism force, thereby distributing load evenly across theback of the segment pack, as illustrated in an exaggerated manner inFIG. 24D.

The implant 10 of some embodiments is designed with angled surfaces tofacilitate self-supporting 3D printing. The implant 10 of someembodiments is also designed with droop-reducing or droop-compensatingfeatures. Additionally, the implant 10 of some embodiments includessegments 12 with minimum-area internal horizontal surfaces to minimizethe amount of support material required during 3D printing. Thesefeatures are illustrated in the view of FIG. 25A. The implant frame 14of some embodiments, as illustrated in the view of FIG. 25B, hasopenings 110 at both ends. The openings 110 permit the inner cavity tobe accessed from either side, increasing ease of support removal andalso make it possible to install the bladder 56 into the inner cavity bya pull-through approach rather than trying to push it in from one end.

FIGS. 26A and 26B illustrate one embodiment of cross webs 112 used inembodiments of the implant 10 to support the individual segments 12 andto stabilize the segments 12 when compressed to keep the segments 12 attheir set heights. The cross webs 112 of this embodiment are planar innature and have bosses to receive and stabilize the segments. Thisreduces the stroke required of the locking mechanism. The cross webs 112are joined top and bottom for direct load transfer in thesuperior-inferior direction rather than sharing load through the frame14. In this way, there are no support points on the frame that can slipoff. As more-clearly shown in FIG. 26B, coils 114 of some embodimentsare grouped in pairs to provide rotational stability without causingexcessive loss of shape-matching ability.

In some embodiments, the plate that compresses the segment stack and theframe 14 are each female threaded with a slotted thread such that theycan both simultaneously engage a locking screw having both left andright hand threads. This is advantageous in that the required axiallength is reduced and the screw (an embodiment of which is illustratedin FIG. 27A) has positive control over the return of the compressionplate instead of relying on the spring force of the segment stack.

FIG. 27B illustrates one embodiment of an inserter end 116 adapted forsecuring and inserting the implant 10 into the intervertebral space. Theinserter end 116 includes sets of opposed claws 118 that engage pocketson the surface of the implant 10. The claws 118 are able to flexinwardly as they enter the pockets due to slits 120 in the inserter end116 that provide compliance and flexibility to the claws 118. Once theclaws 118 are fully engaged in the pockets, a center portion 122 of theinserter is advanced such that the claws 118 can no longer collapseinwardly to release the implant 10. The implant 10 is thus retaineduntil the center portion 122 is withdrawn.

Because multiple items (the feed tube of the bladder 56, the lockingdriver, and the claw expander) have to fit through the inserter end 116,radial space is at a premium. Accordingly, in some embodiments, drivinginterfaces that can transmit relatively large torques while occupyingrelatively little radial space are used. FIG. 28A shows one embodimentthat uses a triple-square drive 124. Hex, Torx, TorxPlus, or somevariation thereof are used in alternate embodiments, as is a driverhaving castellations on the face thereof.

FIG. 28B shows a perspective view of one embodiment of an inserter 126(with the inserter end 116 omitted). To permit proper placement of theimplant 10, it is important to be able to hammer on the back of theinserter 126 without crushing the feed tube of the bladder 56 and torotate the driver to activate the implant shape-locking mechanismwithout twisting up the feed tube of the bladder 56 or depressurizingthe bladder 56. The inserter 126 of FIG. 28B achieves these objectivesby having the top face of the inserter 126 open such that a feed tube128 can exit from the drive and out to the side without passing througha hammering surface 130.

A thumb wheel 132 engages the driver and allows for initial tighteningof the locking mechanism by continuous rotation. For final tightening, acounter-torque is attached to flats 134 of a tail of the instrument anda slotted driver is introduced, still allowing the feed tube 128 to passand remain under pressure. The slotted driver is limited to a smallrange of angular motion to prevent the feed tube 128 from being shearedoff. Accordingly, final tightening is an incremental process.

FIG. 29A shows an alternate version of the inserter 126. In thisembodiment, a gearbox 136 is used to move the rotation connection off tothe side of the feed tube 128. A cap for hammering is provided to theback of the inserter 126. Another solution, as shown in FIG. 29B wouldutilize an inserter 126 similar to that of FIG. 28B, but fits the thumbwheel 132 with a torque-limiting clutch and then uses a wrench 138 ofsome sort to rotate the thumb wheel to achieve final torque. In theembodiment of FIG. 29B, it is important that the clutch not overtightenthe locking mechanism, but always be able to unlock it. The clutch faceshown in FIG. 30A has different entry and exit angles to the depressionsin the race, thus allowing for different release torques in the forwardsand backwards directions.

FIG. 30B illustrates an alternate version of the inserter 126. In thisembodiment, the inserter 126 has a dual-state handle 140 to protect thefeed tube 128 from hammering when the handle 140 is in a straightposition, but providing improved access to a driver 142 when the handle140 is rotated out of the way.

As illustrated in FIG. 31 , the inserter 126 of some embodiments isdesigned such that it does not need to be detached from the implant 10before post packing the implant 10 with bone graft or the like. Instead,after the shape of the implant 10 has been locked, the driver and thebladder 56 can be removed through the internal portion 122 that expandsthe claws 118 to engage the implant 10. Some sort of fusion-promotingsubstance can then be packed into the implant through the lumen of theinternal portion 122.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims, rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed and desired to be secured by Letters Patent is:
 1. Amethod for using an expanding, conforming interbody implant, comprising:affixing an expanding, conforming interbody implant to an inserter, theimplant comprising: a frame; a first plurality of endplate-contactingsegments adapted to each independently extend a variable amount in asuperior direction from the frame; a second plurality ofendplate-contacting segments adapted to each independently extend avariable amount in an inferior direction from the frame; and a lockingmechanism adapted to lock the first plurality of endplate-contactingsegments and the second plurality of endplate-contacting segments in avariety of independently extended positions, whereby eachendplate-contacting segment of the first and second plurality ofendplate-contacting segments contacts and supports bone adjacent theexpandable, conformable interbody implant; placing the implant in adesired location using the inserter while the first and secondpluralities of endplate-contacting segments are in a retracted position;supplying a force that causes each of the first and second pluralitiesof endplate-contacting segments to extend and generally conform tosurfaces above and below the implant; and engaging the locking mechanismto secure the first and second pluralities of endplate-contactingsegments in a variety of extended and conforming positions.
 2. Themethod as recited in claim 1, wherein the first plurality ofendplate-contacting segments is adapted to contact and collectivelyconform to an inferior endplate of a first vertebral body and whereinthe second plurality of endplate-contacting segments is adapted tocontact and collectively conform to a superior endplate of a secondvertebral body.
 3. The method as recited in claim 2, wherein a loadbetween the inferior endplate and the superior endplate is substantiallyequally distributed among the first and second pluralities ofendplate-contacting segments.
 4. The method as recited in claim 1,wherein the locking mechanism exerts a lateral compression force amongthe first and second pluralities of endplate-contacting segments.
 5. Themethod as recited in claim 1, wherein the locking mechanism exerts alateral compression force between the first plurality ofendplate-contacting segments, the second plurality ofendplate-contacting segments, and a plurality of cross webs.
 6. Themethod as recited in claim 1, wherein the first and second pluralitiesof endplate-contacting segments have a limited amount of lateral motionwithin the frame before the locking mechanism is engaged to lock thefirst and second pluralities of endplate-contacting segments in theirextended positions.
 7. The method as recited in claim 1, wherein whenthe first and second pluralities of endplate-contacting segments are ina retracted position, the implant has a smaller vertical profile forinsertion.
 8. The method as recited in claim 1, wherein the first andsecond pluralities of endplate-contacting segments are each interlockedwith adjacent segments while permitting relative superior-inferiormotion therebetween.
 9. The method as recited in claim 1, wherein thefirst and second pluralities of endplate-contacting segments eachcomprise a plurality of segments extending along a length of theimplant.
 10. The method as recited in claim 9, wherein the first andsecond pluralities of endplate-contacting segments each comprise aplurality of segments extending across a width of the implant.
 11. Themethod as recited in claim 1, wherein the first and second pluralitiesof endplate-contacting segments comprise a stiffness approximating thestiffness of vertebral bone.
 12. The method as recited in claim 11,wherein the first and second pluralities of endplate-contacting segmentscomprise a coil pack construction.
 13. The method as recited in claim 1,wherein the implant is formed of biocompatible substances.
 14. Themethod as recited in claim 1, further comprising an expansion mechanismadapted to apply a superior-directed force to each of the firstplurality of endplate-contacting segments and an inferior-directed forceto each of the second plurality of endplate-contacting segments beforethe locking mechanism is engaged.
 15. The method as recited in claim 14,wherein the expansion mechanism is adapted to continue providing thesuperior-directed force and the inferior-directed force while thelocking mechanism is engaged.
 16. The method as recited in claim 14,wherein the expansion mechanism comprises a bladder disposed in aninternal cavity of the implant.
 17. The method as recited in claim 14,wherein the expansion mechanism comprises a mechanism selected from thegroup consisting of: a bladder; a plurality of corrugated layers adaptedto be moved between nested and offset positions; a plurality of springs;a wire disposed on a plurality of pulleys; a plurality of threadedcylinders; and a plurality of dimpled layers adapted to be moved betweennested and offset positions.
 18. The method as recited in claim 1,wherein the frame comprises openings on opposite ends thereof to permitaccess to an internal space of the implant.
 19. The method as recited inclaim 1, wherein the implant is adapted to permit application ofincreased forces in any of an anterior area, a posterior area, a rightlateral area, or a left lateral area.